Experimental studies to determine the physico-mechanical characteristics of soils improved with special hydraulic binders

The complexity of the construction works and site conditions, combined with environmental factors, led to the necessity of using special mineral binders with physical and chemical properties superior to the usual binders. Taking into account the above arguments, the paper presents the results of experimental laboratory studies in order to determine the physical and mechanical characteristics of soil used for a road embankment, after improvement with a special lime-based hydraulic binder. Since improvement recipes vary from one soil to another, it is important to always determine the characteristics after treatment. Also, the method of mixing the binder and soil decisively determines subsequent performance. As part of a larger study aiming at assessing the various factors of influence on the treated soil characteristics, two comparative studies were carried out, each consisting in the recipe formulation using 3 different binder ratios, the difference being given by the parameters used for specimen compaction: normal or modified Proctor test. The study followed the influence of the mechanical compaction work on the mechanical behaviour of the specimens over time after different times of curing

Monopile foundation under lateral cyclic action. Numerical modelling

Foundation of an off-shore wind mill is submitted throughout its existence to a very high number of cycles coming from lateral actions such as waves or wind. These actions have a strong aleatory character which makes them very hard to predict, quantify and analyse. Therefore, in current design practice, these actions are being considered as pseudo-static force at their maximum values, with the cyclic phenomenon being neglected. This can lead to an inappropriate design of the foundation, which could have a negative impact on the future structure. This type of structure is generally built on a monopile foundation, a single, large diameter pile, which will be submitted to thousands lateral cycles. The pile diameter plays an important role, influencing the behaviour of the entire structure. Centrifuge experiments on small-scale models are very useful to study such complex problem as piles under lateral cyclic loads. Several researches have been carried out internationally and the results can be used for calibrating numerical models, which is obviously a more accessible method of design, compared to an experimental approach. This has been precisely the starting point of this paper. The purpose of the present paper is to analyse the influence of the pile diameter, by using a FEM a numerical model, previously calibrated based on centrifuge experiments carried out at IFSTTAR Nantes. For the numerical modelling the software CESAR-LCPC 3D has been used. Several pile diameters have been considered, as follows: 0.72 m, 1.08 m, 1.44 m, 1.80 m, 2.16 m and 2.52 m. The results are taking into account the lateral displacement and bending moment of the piles, for static and cyclic loading. The main objective was to determine the stabilisation rate of the most important two design elements (pile head displacement and maximum bending moment) after “n” cycles and to eventually conclude the diameter value beyond which no more influence of cycles is recorded. The numerical model considered 15 cycles and the results have been used extrapolated in order to determine the cycle “n” of stabilisation (for displacement and bending moment)

Seismic Behavior of Micropiles and Micropiled Structures Used for Increasing Resilience: A Literature Review

The aim of this paper is to present the relevant information and development available in the scientific literature regarding the seismic behavior of micropiles (MPs) and micropiled structures (MPed). The seismic behavior of MPs is not very well studied, but MPs are used in retrofitting of old buildings and for new resilient buildings, and in terms of seismic behavior they have a high potential. Additionally, their association with seismic dampers for improving the seismic behavior of buildings is not yet fully studied and it represents a major topic of interest for both new structures and historical monuments. After the introductory part, the paper describes all relevant information regarding MPs, as types and technology, seismic behavior, applications for increasing seismic resilience, and experimental and numerical modeling

Monopile foundation under lateral cyclic action. Numerical modelling

Foundation of an off-shore wind mill is submitted throughout its existence to a very high number of cycles coming from lateral actions such as waves or wind. These actions have a strong aleatory character which makes them very hard to predict, quantify and analyse. Therefore, in current design practice, these actions are being considered as pseudo-static force at their maximum values, with the cyclic phenomenon being neglected. This can lead to an inappropriate design of the foundation, which could have a negative impact on the future structure. This type of structure is generally built on a monopile foundation, a single, large diameter pile, which will be submitted to thousands lateral cycles. The pile diameter plays an important role, influencing the behaviour of the entire structure. Centrifuge experiments on small-scale models are very useful to study such complex problem as piles under lateral cyclic loads. Several researches have been carried out internationally and the results can be used for calibrating numerical models, which is obviously a more accessible method of design, compared to an experimental approach. This has been precisely the starting point of this paper. The purpose of the present paper is to analyse the influence of the pile diameter, by using a FEM a numerical model, previously calibrated based on centrifuge experiments carried out at IFSTTAR Nantes. For the numerical modelling the software CESAR-LCPC 3D has been used. Several pile diameters have been considered, as follows: 0.72 m, 1.08 m, 1.44 m, 1.80 m, 2.16 m and 2.52 m. The results are taking into account the lateral displacement and bending moment of the piles, for static and cyclic loading. The main objective was to determine the stabilisation rate of the most important two design elements (pile head displacement and maximum bending moment) after “n” cycles and to eventually conclude the diameter value beyond which no more influence of cycles is recorded. The numerical model considered 15 cycles and the results have been used extrapolated in order to determine the cycle “n” of stabilisation (for displacement and bending moment)

Experimental investigation of thermal vehicular environment during the summer season

International audienceThermal comfort evaluation for vehicle occupants is very complicated due to the transient nature and non-uniformity of the vehicle interior. The thermal sensation of an automobile occupant is affected by the surrounding environment. Furthermore, the existing standard was developed for steady state and controlled conditions and it utilizes three evaluation indices, some of which are not adapted for this complex environment. In this article, the three standardized indices are compared in terms of thermal comfort, for a passenger vehicle in summer season. The results show that the mean values of the PMV/PPD model calculated at a single point with Comfort Sense equipment are far from the TSV mean values which were collected in questionnaires, while the t(eq) index which was calculated with an advanced thermal manikin are closer to the TSV comfort votes. This may be explained by the fact that the TSV and t(eq) consider the sensation for each body part at the local level. For a correct evaluation of the thermal comfort in non-uniform and transient environments like in vehicles, it is not enough to measure a single point